Abstract â–¡ 85

It has been suggested that one of the elements of Sudden Infant Death Syndrome (SIDS) may be subtle defects in the brainstem neural circuitry which control respiration and/or cardiovascular stability particularly during sleep.

Brainstems from 7 control cases ranging in postnatal age from 0 to 7 months were selected from archive material. 10 SIDS NBW cases ranging in postnatal age from 2 to 7.5 months and 8 SIDS LBW ranging in postnatal age from 2 to 8 months were also incorporated into the study. Verification of the cause of death was based on a comprehensive postmortem carried out by a specialised pediatric pathologist. Each brain was removed from 10% buffered formalin, washed in cold running water and the brainstem dissected out, dehydrated through increasing concentrations of alcohol and embedded in methyl methacrylate resin. Each resin block was serially sectioned at 25µm and every 4th section (the first section chosen at random between sections 1 to 4) stained with Haematoxylin and Eosin. The volume of each nucleus (arcuate, hypoglossal and reticular formation nucleus) was estimated using the Cavalieri's Principle Using the optical brick technique, the numerical density for neurons and glial cells was estimated for each nuclei. The total number of neurons and glial cells present in each nuclei was estimated by multiplying the volume of the nucleus by the numerical density. Results were analysed between groups using the Mann Whitney Rank sum test and over age using linear regression analysis.

The arcuate nucleus showed no significant difference in total numerical density between control and SIDS NBW (p=0.962) or SIDS LBW (p=0.613) cases. There was no significant difference in neuronal numerical density between control and SIDS NBW (p=0.780) or control and SIDS LBW (p=0.536) cases. There was a difference between SIDS NBW and SIDS LBW cases (p=0.0575) which failed to reach statistical significance.

Analysis of the hypoglossal and reticular formation nuclei are ongoing and results will be presented at the meeting.

Instability in a rapidly developing neural system may cause infants to be vulnerable to sudden death under conditions which stress the adaptability of those systems. A subtle delay/arrest in the brainstem neural circuits may impinge on the stability of respiratory and cardiovascular functions.